I read this as EK issued QF flight number, say QF1/2/9/10 in which case it's irrelevant who issued the ticket just the operating carrier and oneworld rules would apply out of LHR (and, I presume, DXB).
Now if it's issued as EK5001/EK5002 etc it should still be OK because on check-in you'd be issued a QF BP for the QF flight number, so the lounge dragons would see that and admit on that.
The only time you'd be in trouble if it's say QF8xxx or whatever an EK codeshare number would be for QF, and that would thus be an EK metal flight, and thus oneworld rules would not apply.
Clear as mud
